Paper sizing agents



July 17, 1962 G. J. BOUGHTON ETAL 3,044,890

PAPER SIZING AGENTS 2 Sheets-Shea?I 1 Filed March 24,` 1959 ESQ@ ainsi@ l Patented July 17, 1962 The present invention relates to paper sizing agents and it is an object of the invention to provide paper sizing agents of improved efficiency, whereby an increased sizing eiect can Ibe obtained as compared with known sizing agents when used in the same amount, or, conversely, a lesser amount of sizing agent can be made to give the same sizing eifect, thereby eecting corresponding savings in sizing costs.

Conventional paper sizing agents often consist of an aqueous dispersion of a rosin, which may be partly saponitied by incorporating an alkali, such as caustic soda, into the rosin dispersion and may also contain a protective colloid, such as casein, `and one or more ller or extender materials, of which kaolin is an example.

It is also known to use so-called soap sizes, which consist essentially of a rosin dispersion so treated with alkalies that the acid-like bodies present in the rosin are substantially completely saponiiied. These are generally inferior in sizing eciency to free rosin dispersion sizes.

It has been -found that conventional paper sizing agents both of the soap size and rosin dispersion size kinds can be greatly bettered in sizing eiiiciency by incorporating into a rosin dispersion a modified rosin product, described in detail below, so as to give what maybe termed a reinforced sizing agent.

In the accompanying drawing, FIG. 1 is a graph showing the percent sizing solids plotted against Cobb degrees; iFIG. 2 is a flow sheet showing the general preparation of the paper sizing agent.

According to the present invention, a method of manufacturing a paper sizing agent comprises the steps of forming a modied rosin ester product with a compound which includes the group adding the modied rosin ester product to -a rosin and forming an aqueous dispersion thereof.

The invention also consists in a paper sizing agent comprising an aqueous `free rosin dispersion containing a modified rosin ester product formed with a compound which includes the group In one Way of carrying into elect the method of the invention, rosin is reacted with an na-unsaturated acid or -anhydride to form a rosin adduct, the latter is esterin tied to form a modified rosin ester product and this is added to rosin and an aqueous dispersion thereof is then formed. In the paper sizing agent so formed, the modified rosin ester product comprises an esteriiied rosin adduct of an m18-unsaturated acid or anhydride.

In another way of carrying into effect the method of the invention, a rosin ester is reacted with an na-unsaturated acid or anhydride to -form a modified rosin ester product and this is added to rosin and an aqueous dispersion thereof is formed. In the paper sizing agent so formed, the modified rosin ester product comprises a rosin ester reaction product of an na-unsaturated acid or anhydride.

In one embodiment of the last-mentioned method of the invention, rosin is reacted with alcohol to Iform the rosin ester. *f

The preparation of the modified rosin ester product essentially involves an addition reaction of the Diels- Alder diene type, in which the conjugated double bond system present in the na-unsaturated `acid or anhydride, i.e. the group combines with an unsaturated bond present in the rosin or rosin ester molecule.

Of the many na-unsaturated acids and anhydrides which will undergo an addition reaction with a rosin or rosin ester, maleic acid, fumarie acid and, especially, maleic anhydride `are preferred in carrying the invention into effect. The other ingredients used in the preparation of the addition reaction product may comprise any rosin which includes colophony and may consist of wood rosin, gum rosin and esteried rosin, the latter being preferred. f

An improved paper sizing agent of the invention may be prepared in the general manner described below in conjunction with the accompanying flow sheet, FIG. 2, which is to be taken as being by way of example.

PREPARATION OF MODIFIED ROSIN ESTER PRODUCTS A lknown quantity of a rosin 1, which expression for this purpose includes any material containing colophony, thereby having an unsaturated bond in the molecule, such as gum rosin or rosin ester gum, is melted and agitated, 2, and a calculated quantity of an a,-unsaturated acid or anhydride, preferably maleic anhydride, 3, is added to the molten and heated rosin and allowed to react therewith for a time sutcient to produce the addition product constituting the desired modied rosin 4. If the rosin reacted with the acid or anhydride is not an esteritied material, the product so obtained is `a rosin adduct 5 and this .is then esteritied by reacting it with an alcohol 6, for example, glycerol. This esteritication step is not necessary when the rosin is already esteried, 1, and is, for example, resin ester gum. Alternatively, the rosin 1 may be esteried rdrst 4by heating and agitating it, 7, Iand reacting it with an alcohol S to produce a' rosin ester or esteriiied rosin 1. The modied rosin ester product 4 so formed need not be used immediately in the preparation of a paper sizing agent and is sufiiciently stable to be stored until required.

PREPARATION OF REINFORCED SiZiNG AGENT A known quantity of rosin 9 is melted, preferably in 'a vessel provided with stirring and heating mechanism, 10, and a predetermined quantity of the modified rosin ester product 4 is added thereto with intensive agitation and the vessel con-tents are vvmaintained at an elevated temperature. Though the modified rosin ester product 4 may be added to the rosin 9 in any proportion, it is suitable for economy reasons and also because an excellent reinforced sizing agent can be so produced to employ a minor proportion of the modified rosin. It has been found that a satisfactory reinforced sizing agent can be prepared, having an excellent sizing efficiency as compared 4with yconventional sizing agents, even free rosin siz ing agents, by incorporating the modified rosin ester product 4 in the rosin 9 in the proportion of 5 te 25% iby weight and preferably approximately 16% by Weight,

The product so obtained is then partially saponiiied by the addition of a small quantity, e.g. 1%, of caustic soda or other alkali in solution 11. If it is desired to include a mineral filler or extender, such as colloidal kaolin, in the reinforced sizing agent, it can be added at this stage 12 (ie. either before or after the partial saponification), preferably by making use of high speed stirring or other intensive agitation 0f the mixture of rosin and modified rosin while so doing.

The next stage in the preparation of the reinforced sizing agent comprises the formation from the rosin mixture described above, with or Without fillers or extenders, of an aqueous dispersion and this is preferably done by slowly adding to the rosin material, while held at an elevated temperature and intensively agitated, an aqueous solution of an alkali, which may conveniently include a protective colloid such as casein 13. While many alkaline materials can be used to prepare the alkaline solution, it has been found that satisfactory results can be obtained by using a solution of caustic soda or other alkali metal hydroxide `or an alkaline alkali metal salt, such as sodium berate. If desired, the solids content of the :aqueous rosin dispersion can then be altered by agitating it, 14, `and adding a calculated quantity of Water thereto, 15; cold water maybe used for this purpose and, at the same time, for cooling the dispersion.

As an alternative to the last stage in the preparation as described above, the aqueous dispersion may be made using an alkaline solution 16 which does not include a protective colloid, and in this case, such a material, conveniently in the form of an aqueous alkaline dispersion of casein or other colloid 18, may be added to the dispersion while undergoing agitation, 17, as a separate step in the preparation. The ingredients of the dispersion are again agitated as by stirring iat high speed and, 'after further dilution with water 19 to adjust the solids content, if desired, the whole may be allowed to cool and the sizing agent 20 so formed can then be stored until ready for use.

In a further modification of the procedure, the material so formed, though itself eminently suitable for use as a reinforced paper sizing agent 20 of high eliiciency, may have a Wax or wax-like material 23 incorporated therein. This can be effected by melting, 22, the wax Z3 and slowly adding it to and rapidly stirring it, 21, into the dispersion and, if desired, following it with a quantity of a preliminary colloid 24, for protecting the product, which constitutes an aqueous alkaline rosin emulsion, from breakdown of the emulsion.

In order that the invention may be readily understood by those skilled in the art, certain preferred embodiments thereof are set out in the following examples, in which Examples 1 to 4 describe the preparation of a modified rosin ester product and Examples 5 and 6 describe the preparation of reinforced sizing agents:

Example 1 200 lbs. of rosin ester gum were melted in a heated and stirrable vessel and maintained at a temperature of approximately 150 C. 100 lbs. of maleic anhydride (i.e. a Weight ratio of 2 parts rosin ester gum to 1 part maleic anhydride) were added to the molten rosin ester gum and the reaction was allowed to proceed to completion for minutes, with the stated tempenature being maintained. The modified rosin ester product so formed was then run ofi to storage and allowed to cool.

Example 2 The procedure of Example l was repeated with the exception that 200 lbs. of rosin representing 2 parts by weight of rosin per 1 part by weight of maleic anhydride) were used in place of the rosin ester gum. When the reaction had gone to completion, the rosin adduct so formed was maintained at a temperature of 150 C. and stirred while 25 lbs. of glycerol (representing l part of glycerol per l2 parts of reaction product) were added to effect esterification of the rosin adduct. The reaction 4 conditions were maintained for approximately 30 minutes and the modified rosin ester product so formed was then run oli to storage and allowed to cool.

Example 3 200 lbs. of gum rosin were melted in a heated and stirrable vessel and maintained at a temperature of approximately C. while 25 lbs. of ethylene glycol (representing 1 part of ethylene glycol per 8 parts of rosin) were added to esterify the rosin. The reaction conditions were maintained for approximately 30 minutes and then, when maintaining the temperature of 150 C. and agitating the vessel contents, 120 lbs. of maleic acid were stirred in and the reaction was allowed to proceed to completion in 30 minutes, whereupon the modified rosin ester product was stored and cooled.

Example 4 The procedure of Example 1 was repeated except that 120 lbs. of fumarie acid were used instead of maleic anhydride.

Example 5 464 lbs. of gum rosin were melted in a steam-jacketed vessel provided with a stirring mechanism suitable for intensively agitating the contents and the molten gum rosin was stirred at Z50-300 revolutions per minute. 46 lbs. of the modified rosin ester product prepared as described in any of Examples 1 to 4 (representing approximately 10% by Weight of the rosin) were added, the vessel and its contents lbeing maintained at a temperature of the order of 14C-150 C.

The mixture of rosinand modified rosin so obtained was then dispersed by high speed agitation in a solution of 10 lbs. of caustic soda dissolved in 7 litres of water,

' which was slowly added to the vessel. The resultant dispersion was then cooled by carefully adding cold water thereto, which water cools the dispersion by evaporation from it, until the temperature was reduced t0 100 C.

In order to include a protective colloid in the rosin dispersion, a lactic casein solution was prepared by dissolving 17 lbs. of casein and 5 lbs. of sodium borate in about 40 litres of water at approximately 80 C. and this was slowly added to the stirred rosin dispersion and the whole was agitatedV at high speed for 5 minutes. The resultant colloid-protected dispersion was diluted with 100 litres of water at 40 C. and further cold water was added to adjust the solids content as required` Example 6 415 lbs. of rosin were melted in a vessel provided with heating means and an agitator, 41 lbs. of modified rosin prepared as described in any of Examples 1 to 4 (representing approximately 10% by weight of the rosin) were added thereto and the mixture was heated to and maintained at a temperature of the order of l40-150 C. with continuous intensive agitation. The mixture of rosin and modified rosin so formed was then emulsied with a solution prepared by dissolving 14 lbs. of sodium borate in 20 litres of w-ater at approximately 80 C., the solution being slowly added to the heated rosin mixture with continuous stirring. Sufficient cold water was then added to the stirred dispersion so formed to reduce its temperature to approximately 100 C.

In order to obtain a reinforced sizing agent which includes a filler having the property of enhancing the whiteness of paper sized therewith Without being detrimental to the sizing property of the resulting sizing agent, lbs. of nely-divided colloidal kaolin were stirred into the rosin dispersion and stirring was continued at high speed (Z50-300 revolutions per minute) for 5 minutes.

A protective colloid solution was prepared by dissolving 5 lbs. of sodium borate and 15 lbs. of casein in 30 liters` of water at a temperature of 70 C. in that order and the resultant lactic casein solution was added to the rosin dispersion and agitated for 3 minutes.

8 lbs. of microcrystalline, parain or other Wax were melted and held at approximately 80 C., slowly added to the rosin mixture and the whole agitated for 3 minutes. 45 litres of a preliminary colloid, conveniently prepared by the process described in British patent specification No. 536,874 were then added to the other ingredients .and again agitation at high speed was carried out for 3 minutes to prepare the desired reinforced kaolin-containing sizing agent, which may be furtherY diluted with cold water, if desired, to adjust the solids content thereof.

The sizing agents of the invention have the considerable advantage of a greatly increased sizing efficiency as compared with conventional rosin sizing agents and soap sizes and sizing efficiencies increased by as muchas 30- 40% are exhibited by sizing agents of the kinds typied by those described in Examples 5 and 6. It is thus possible to manufacture paper and related products whichare similar in properties to paper products sized with conventional agents and to employ 30`-40% less sizingfagents, thereby obtaining a substantial reduction in the cost of materials. Alternatively, paper and like products can be sized to a greater extent at no extra cost by employing the more efficient sizing agents of the invention. The invention also has the advantage that it can readily be carried out without requiring the use of any materials which are particularly expensive or are unusual in the manufacture of sizing agents.

Referring to FIG. 1, there is shown a graphic representation of percent sizing solids to bre plotted against Cobb degrees, which is a standardV test for water absorp tion wherein the Cobb gure is the amount of water in grams taken out by one square meter of paper surface in one minute. The continuous line represents values obtained with a sizing agent of the invention, the broken line represents values obtained with a conventional free rosin size and the dot-dash line represents values obtained with a soap size made with a modiied rosin.

Comparing Cobb values obtained with equal percentages of sizing solids, it will be observed that at 2% sizing solids, Cobb values of 12.7, 13.8 and 14.5 are given by the novel sizing agent, the free rosin size and the soap size respectively. At half of this tigure, i.e. 1% sizing solids, the Cobb values are respectively 14.5, 15.2 `and 19.0, demonstrating that the novel sizing agent gives a better Cobb value than free rosin size and an appreciably better Cobb value than soap size. The improved performance of the sizing agent of the invention 6 in a weight ratioof 2 parts of rosin to at least 1 part of a material of the saidV group, maintainingV the thusformed mixture at a temperature of the order of 140 to 150 C. and for a time sufficient to complete the formation of a chemical reaction productvconstituted by a rosin adduct, adding an alcohol selected from the group is demonstrated even more convincingly at 0.5% sizing solids, Where the Cobb values given are, respectively, 16.0, 18.2 and 25.7, while at 0.3% sizing solids, the Cobb values are, respectively, 18.8, 23.2 and 33.8.

If equivalent sizing effect is considered instead, it will be observed that a Cobb value of 14.5 is given using 1.0% sizing solids with the size of the invention, 1.3% sizing solids with the free rosin size and 2.0% sizing solids with the soap size. In other words, to obtain a Cobb value of this order, it is necessary to use the sizing agent of the invention in an amount of approximately 3A the amount of the free rosin size and 1/2 the amount of the soap size. Again, a Cobb value of 16.0 is given with 0.5% sizing solids with the size of the invention, 0.8% sizing solids with the free rosin size and 1.5% sizing solids with the soap size; a Cobb Value of 18.0 is given with 0.33% sizing solids with the size of the invention, 0.53% sizing solids with the free rosin size and 1.15% sizing solids with the soap size.

The values shown in the accompanying graph were obtained with paper samples prepared with the sizing agents mentioned from bleached sulphite 40 S.R., having a pH of 5.0 at 0.8% consistency.

We claim:

1. A method of manufacturing a paper sizing agent, which consists essentially of the steps of melting a rosin, admixing therewith a material selected from the group consisting of a,unsaturated acids and their anhydrides consistingof glycerol and ethylene glycol to the reaction product and maintaining the mixture thus formed at a temperature of the order of to 150 C. to effect complete esterication of the reaction product, thereby to convert the rosin adduct into a rosin ester product, and cooling the resultant rosin ester product, melting a quantity of rosin, agitating the molten rosin, adding 'a quantity of the aforesaid rosin ester product to the molten rosin while continuing agitation thereof, the rosin ester product constituting from 5 to 25% by weight of the molten rosin, agitating the resultant mixture of molten rosin and rosin ester product, adding an aqueous dispersing medium thereto and recovering the thusaformed aqueous, rosin-ester-product-containing rosin dispersion.

2. A method of manufacturing a paper sizing agent, which consists essentially of the steps of melting -a rosin, admixing maleic anhydride therewith in a weight ratio of 2 parts of rosin to 1 part of maleic anhydride, maintaining the thus-formed mixture at a temperature of about C. for a period of about 30 minutes thereby to form a chemical reaction product constituted by a rosin adduct of maleic anhydride, adding glycerol to the reaction product in a weight ratio of 1 part of glycerol to 12 parts of the reaction product and maintaining the mixture at a temperature of about 150 C. to esterify the reaction product and thereby convert it into a rosin ester product, and cooling the thus-formed rosin ester product, melting a quantity of rosin, agitating the molten rosin, adding a quantity of the rosin ester product yto the molten rosin while continuing agitation thereof, the rosin ester product constituting from 5 to 25 by weight of the molten rosin, agitating the resultant mixture of rosin and rosin ester product, adding an aqueous caustic soda solution thereto and recovering the thus-formed aqueous, rosin-ester-product-containing rosin dispersion.

3. The method of claim 2, wherein the mixture of rosin and rosin ester product is maintained at a temperature of 140 to 150 C. during the agitation thereof.

4. The method of claim 1, wherein the mixture of rosin and the material of the irst-mentioned group is'maintained at a temperature of approximately 150 C. for a period of about 30 minutes.

5. The method of claim 1, wherein the rosin ester product is added to the molten agitated rosin in an amount of about 10% by weight thereof.

6. The method yof claim 1, wherein the mixture of rosin and rosin ester product is maintained at a temperature' of the order of 140 to 150 C. during the agitation thereof and the aqueous dispersion is cooled by adding cold water thereto in an amount suicient to reduce the temperature to 100 C. by evaporation.

7. The method of claim 1, wherein the aqueous dispersing medium contains caustic soda and a protective colloid.

8. The method of claim 1, wherein the aqueous dispersing medium contains caustic soda and wherein a protective colloid is added to the aqueous rosin dispersion.

9. The method of claim l, wherein the aqueous, rosinesterproductcontaining rosin dispersion is agitated, a quantity of a wax selected from the group consisting of paraffin wax and microcrystalline wax is melted and the molten wax is dispersed into the rosin dispersion.

10. A free rosin paper sizing agent consisting essentially of an aqueous dispersion of a rosin containing 5% to 25 by weight, relative to the rosin, of a rosin ester product obtained by melting a rosin, admixing therewith a material selected from the group consisting of ,-unsaturated acids and their anhydrides in a Weight ratio of 2 parts of rosin to at least l part of a material of the said group, maintaining the thus-formed mixture at a temperature of the order of 140 to 150 C. and for a time suicient to complete the formation of a chemical reaction product constituted by a rosin adduct, adding an alcohol selected from the group consisting of glycerol and ethylene glycol to the reaction product and maintaining the mixture thus formed at a temperature of the order to 140 to 150 C. to eiect complete esterication of the reaction product, thereby to convert the rosin adduct into a rosin ester product, and cooling the resultant rosin ester product.

11. A free rosin paper sizing agent consisting essentially of an aqueous dispersion of a rosin containing 5% to 25% by weight, relative to the rosin, of a rosin ester product obtained by melting a rosin, adrnixing maleic anhydride therewith in a weight ratio of 2 parts of rosin to 1 part of maleic anhydride, maintaining the thusformed mixture at a temperature of about 150 C. for a period of about 30 minutes thereby to form a chemicd reaction product constituted by a rosin adduct of maleic anhydride, adding glycerol to the reaction product in a weight ratio of 1 part of glycerol to 12 parts of the re- 8 action product and maintaining the mixture at a temperature of about 150 C. to esterify the reaction product and thereby convert it into a rosin ester product, and cooling the thus-formed rosin ester product.

12. The paper sizing agent of claim 10, wherein the rosin dispersion contains the rosin ester product in an amount of 10% by Weight of the rosin.

13. The paper sizing agent of claim 10, wherein the rosin dispersion contains a protective colloid.

14. The paper sizing agent of claim 10, wherein the rosin dispersion contains a wax selected from the group consisting of paraiin wax and microcrystalline wax.

References Cited in the le of this patent UNITED STATES PATENTS 2,628,918 Wilson Feb. 17, 1953 2,791,578 Drechsel May 7, 1957 2,797,167 Kolodny June 25', 1957 2,881,084 Watkins Apr. 7, 1959 FOREIGN PATENTS 536,874 Great Britain May 30, 1941 

1. A METHOD OF MANUFACTURING A PAPER SIZING AGENT, WHICH CONSISTS ESSENTIALLY OF THE STEPS OF MELTING A ROSIN, ADMIXING THEREWITH A MATERIAL AND SELECTED FROM THE GROUP CONSISTING OF A,B-UNSATURATED ACIDS AND THEIR ANHYDRIDES IN A WEIGHT RATIO OF 2 PARTS OF ROSIN TO AT LEAST 1 PART OF A MATERIAL OF THE SAID GROUP, MAINTAINING THE THUSFORMED MIXTURE AT A TEMPERATURE OF THE ORDER OF 140* TO 150* C. AND FOR A TIME SUFFICIENT TO COMPLETE THE FORMATION OF A CHEMICAL REACTION PRODUCT CONSTITUTED BY A ROSIN ADDUCT, ADDING AN ALCOHOL SELECTED FROM THE GROUP CONSISTING OF GLYCEROL AND ETHYLENE GLYCOL TO THE REACTION PRODUCT AND MAINTAINING THE MIXTURE THUS FORMED AT A TEMPERATURE OF THE ORDER OF 140* TO 150* C. TO EFFECT COMPLETE ESTERIFICATION OF THE REACTION PRODUCT, THEREBY TO CONVERT THE ROSIN ADDUCT INTO A ROSIN ESTER PRODUCT, AND COOLING THE RESULTANT ROSIN ESTER PRODUCT, MELTING A QUANTITY OF ROSIN, AGITATING THE MOLTEN ROSIN ADDING A QUANTITY OF THE AFORESAID ROSIN ESTER PRODUCT TO THE MOLTEN ROSIN WHILE CONTINUING AGITATION THEREOF, THE ROSIN ESTER PRODUCT CONSTITUTING FROM 5 TO 25% BY WEIGHT OF THE MOLTEN ROSIN, AGITATING THE RESULTANT MIXTURE OF MOLTEN ROSIN AND ROSIN ESTER PRODUCT, ADDING AN AQUEOUS DISPERSING MEDIUM THERETO AND RECOVERING THE THUS-FORMED AQUEOUS, ROSIN-ESTER-PRODUCT-CONTAINING ROSIN DISPERSION. 